Cathode-ray ignition analyzer



Aung 8, 1944 P. s. CHRIST/ALDI 2,355,363

CATHODE-RAY IGNITION ANALYZER Filed sept. 29, 1942 4 sheets-sheet 1 ug- 8, 1944- P. s. cHRls-rALDl 2,355,363

CATHODE-RAY IGNITION ANALYZER Filed sept. 29, 1942 4 sheets-sheet 2 P. s. cHRlsTALDl 2,355,363

CATHODE-RAY IGNITION ANALYZER Filed Sept. 29, 1942 4 sheets-sheet s Aug. 8, 1944.

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Aug 8, 1944- P. s. cHRlsTALDl 1 2,355,363

CATHODE-RAY IGNITION ANALYZER Filed sept. 29, 1942 4 sheets-sheet 4 105 100 a i L mils/vraie.

time base.

Patented Aug. 8, 1944 UNITED STATES PATENT 2,355,363 canone-mr rGNmoN Ammazza Peter S. Christaldi, Wood-Ridge, N. J., assignor to Allen B. DuMont Laboratories, Inc., Passaic,

N. J., a corporation of Delaware Application September 29, 1942, Serial No. 460,142

19 Claims. (Cl. 171-95) 'Ihis inventionis for a device or system that is particularly useful for analyzing the spark plug ignitions of internal combustion motors, such as aircraft engines, for example, by applying signals from the spark plugs to cathode-ray tubes through circuits that amplify the signals and so relate them that signals from any spark plug can be identified and enlarged so as to be readily ex amined visually without loss of time.

Heretofore the investigation of spark plugs on airplane engines has in many cases required removal of complicated ignition shielding systems around the spark plugs asl well as removal of the spark plugs themselves.

By the present invention the individual spark plugs can be tested without removing them or their shields, and diilerent sorts of defects can be ascertained in the ignition system, such as cracked spark plugs, faulty air gaps, poor insulation or short circuits, load conditions of engine, valve adjustments and richness of fuel, etc.

' In carrying out the invention, only a single circuit connection is required from this device to the ignition system to be tested. Signals from all spark plugs operating from one magneto can be viewed at one time on a cathode-ray tube, and any spark plug which appears to be abnormal can be selected and shown on an enlarged scale where it can be examined in more detail. At the same time its signal can be intensified on the small scale for certainty of identification when it is being examined on the large scale.

Briefly, the principle upon which the invention operates is that asawtooth signal is generated and synchronized to provide a sawtooth sweep for each revolution of the accessory or distributor shaft ofthe engine of which the spark plugs are to be tested. This sawtooth sweep is applied to the horizontal de ection plates or coils of a cathode-ray tube to provide a horizontal At the same time, signals from the magneto, consisting of discharges from all of the spark plugs in the sequence of their firing order, are applied to the vertical deilecting plates or coils of this cathode-ray tube so that the spark plug discharges are all shown on a small4 scale I as they occur in sequence in the-engine.

Since all the spark plugs discharge during the rise in voltage of each sawtooth interval, each spark plug discharges within an interval of time represented by the time of one sawtooth divided by the number of spark plugs. Any one of the discharges or signals can be selected at its proper interval and utilized for control and identiilca tion purposes inthe system, as will be explained in more detail later.

Another cathode-ray tube is provided with a sweep circuit so timed that the electronbeam sweeps across horizontally during a time interval equal or approximately equal to a single discharge of a spark plug, and can be synchronized to the interval of -any spark plug of the series.

At the same time a signal of the desired spark plug is applied to the vertical deecting plates of. this tube so that the signal can be more closely examined, while the corresponding signal on the other tube is simultaneously intensied for identiilcation purposes.

The invention may be' understood from the description in connection with the accompanying drawings. in which:

Figs. la and 1b are end views of cathode-ray tubes showing, respectively, a signal from one spark plug on an expanded time scale and all the signals from all the spark plugs operating from one magneto of an internal combustion engine, on a compressed time scale;

Fig. 2 is a block diagram illustrating an embodiment of the invention. The blocks are correspondingly indicated on the detail drawings;

Fig. 3 is a circuit diagram of connections t the cathode-ray tube I;

Fig. 4 is a diagram showing a recurrent sweep circuit and amplifier for the cathode-ray tube 2;

Fig. 5 is a diagram of connections for generathorizontal deiiecting plates 5 and 6, and grids 'l and 8, respectively.

A lead I0 extends from the distributor D for spark plugs of an internal combustion engine which is represented as having eighteen spark plugs, although engines of different numbers of spark plugs as well as other recurrent phenomena can be tested.

In the block diagram shown in Fig. 2, the lead I0 is shown connected to a vertical amplifier II for the tube I and a vertical amplifier I2 for the tube 2 and an optional device I3 which is adapted to produce a recurrent sweep signal for the tube I. Amplifiers I4 and I5 are shown diagrammatically in Fig. 2 for the horizontal deflecting plates 5 and-6, respectively. A horizontal sweep sawtooth generator I6 is synchronized by signals from a contacter driven by the auxiliary shaft vamplifier Il and the recurrent sweep I3 or impulse sweepls at will. A switch 20a is provided in the connection from the unit 'I8 to the grids l and 8. Itis ganged with switch 20.

In Fig. 3 the vertical amplifier Il of Pis. 2 is shown with the lead Il which is from t distributor D. It is connected by blocking condenser 22 to the first grid f the duplex triode amplifier, and the usual grid leak Il is provided. The amplified signal for one of the .plates 2 of the cathode-ray tube I is taken of! f the first plate of the diode 28 by means of the lead 2l, and the other signal in phase opposition is taken oi'f of the other plate by means of the lead 26. The vertical positioning resistance is provided as a source of positioning potential.

The horizontal ampliner Il of Pig. 2 is also shown in Fig. 3 with the switch 2l by which it may be connected to either one of the two horizontal sweep generators I! or Il of Fig. 2 for the cathode-ray tube I. The switch Il is connected to the grid II of an amplifier tube II of which the cathode is loaded to constitute an impedance transformer. The signal from this cathode is applied by a coupling capacitor, a gain control resistnr, and lead I! to a grid of the duplex triode ampliiler 3l that is similar to the duplex triode amplifier 23. Tube u is connected to the horizontal deflecting plates l of the tube I in a similar way to supply the amplified sweep signal to these plates from the generator Il or Il, depending upon the Iposition of the switch 2l.

When the switch is moved to connect the grid 30 with the terminal ll' of the lead ll. the horizontal plates l of the tube I are connected to the single sweep circuit Il of Fig. 2. the diagram of connection for which is shown in Fig. 3. This circuit is made up of charging capacitors l! and I2, as selected by switch 4I, charging resistors I1 and 31', gas triode Il, diode 44', and potential divider Il. With diode Il' eliminated from the circuit, the gas triode 44 and its associated components operate as a generator of recurrent sawtooth waves in a manner well known. When the diode t4' is placed in the circuit and the potential is adjusted at Il' until, in the absence of signals at the grid of tube Il. oscillations cease, the application of a positive pulse to the grid of tube 44 will result in the generation of a single linear sweep of the linear time base. When switch II is connected to capacitor. It, signals of lower frequency are generated than when it is connected to capacitor I2. In the former condition, switch IIa which is ganged with 4switch 4I makes connection to capacitor CII, in order that lower frequency signals can be coupled from tube lla to the grid of gas triode 'Il to permit positive initiation of single linear sweeps. 'I'he details of tube lla are further explained in connection with Fig.

When the switch 2l is turned to the 3l', a recurrent sawtooth wave is applied to the horizontal deflection plates l of the cathode-ray tube I, to provide a linear time base of suiiicientl'y high frequency to permit tbesuperposition of the individual spark plug'discnarges for purposes of comparison. This sawtooth wave is generated in the recurrent sweep generator Il of Fig. 2. which is shown in more detail in Ilm-3. It consistsof the gas triode Il, charging capacitors Il whichcanbe cutinby switch II' andlcharging resistors l2, potentiometer l) for the control vof amplitude of synchronizing dln, and coupling capacitor Il through'which cm be applied tothe gridoftubellsignalsforsynehroniaingthe saw- Ihe bldckjll in Fig. 2 indicates the amplifier for applied to uw ver 'f' deilecti'on plates' terminal same input signals are amplined by it.

The diagram of connections for the horizontal sweep sawtooth generator Il of Fig. 2 which generates a recurrent sweep signal for the cath-- ode-ray -tube I is shown in Fig. 4 together-with the ampliner il for this horizontal sweep sawtooth signal. Positive potential is applied through v'tl'ie charging resistors II, one of which is variable to the 'plate of the gas filled triode II, and charging capacitors l2 of dierent sizes are provided to be connected between the resistors Il and the cathode, so that sawtooth waves of different frequencies may' be generated. This sawtooth wave generator is synchronized by signals from a contactor synchronous with the masneto M, or by signals from the magneto itself, applied through the capacitor Il with the grid rpotentiometer M connected to ground. This synchronized sawtooth wave is applied throughthe lead ll to the grid of the amplifier Il, which has a loaded cathode I1, thus providing an impedance transformer. A lead connects from this cathode through a capacitor Ol and potentiometer Il' to the first grid of the duplex'triode 1l of which the cathodes are connected together so that the plaies thereof will deliver sawtoothwave shaped voltages in phase opposition to the reapective horizontal deilecting plates of the cathode-ray tube 2 in the usual way.

'I'he sawtooth wave generated in the recurrent sweep circuit (Fig. 4) is also taken oi! by the lead 'Il and applied to block I1 of Fig. 2, which is shown in detail in Fig. 5. This sawtooth wave is applied to the grid of g. triode ampliner 1l. The amplified sawtooth signal from the tube Il i1 applied through a blocking capacitor 11 to the cathode follower impedance transformer 1l, having` a positive grid bias supplied by potential divider 1I. This signal is applied through the lead l0 to a diode clipper II to produce a socalled Z-wave which may modulate the intensity of the cathode-ray beam of tubes I and 2. It will be more completely described later. This Z-wave is amplified by being applied through the blocking capacitor II to the grid of the tube. Il which is provided with a grid .leak Il. The amplified signal then passes through the shorttime-constant coupling network made up of capacitor Il or Il and Il' in parallel, chosen by switch IIC, and resistors t1 and Il' in parallel. Diode Il is a surge limiter to prevent the passage of negative polarity surges. .The diiferentiated signal is then applied to the grid of the cathode follower tube Il and thence passes to the clipping tube Il. It is then passed through a capacitor Il to a squaring clipper i2 from which the squared signal is taken of! to the grids of the cathode-ray tubes I and 2 by means of the lead Il.

-`The operation of the device will be described in detail'where it isused to testthesparkplugs of an internal combustion engine having eighteen spark plugs, energized from a common magneto. that is provided with the usual auxiliary shaft that revolves once during the interval. in which .all of the spark plugs iire. This auxiliary shaft assasos the generation of the sawtooth wave (Fig. 6b). The wave forms of Fig. 6 are shown in a manner to illustrate the several steps oi' wave shaping. The polarities of some of the waves shown may, in theoperating circuit, be inverted from those shown in Fig-6. The wave of Fig. 6 is amplified by the amplifier I6 (Fig. 2), which comprises amplifiers 66 and 'I0 (Fig. 4), and is applied to the horizontal defiecting plates of cathode-ray tube 2. At the same time, signals from the terminals of the distributor D (Fig. 2) for all the spark plugs are applied in sequence during each sweep interval to the vertical deiiection plates 4 of the cathode-ray tube 2 -after having been amplified by the amplifier I2 (Fig. 2) which is similar to the amplifier I4 shown in Fig. 3. 'I'his gives a visual indication such as is shown in Fig. 1b and Fig. 6i, the showing in Fig. 6i being spaced wider and on a smaller vertical scale than that in Fig. 1b. Simultaneously, the vertical defiection signal is amplified by the ampliiier I I and applied to the vertical deflection plates 3 of cathode-ray tube I.

'Ihe sawtooth signal (Fig. 6b) is at the same time passed through shaping circuits I'I and differentiating circuits I8 (Figs. 2 and 5) and applied to the grids of the cathode-ray tubes I and 2. In order to do this'the signals are taken off by means of lead l5 (Fig. 4) and amplified by the tube I6 (Fig. 5) thus producing a sawtooth Wave like Fig. 6b, but amplified. The tube 18 is used to provide a low impedance signal source to feed the clipper 8l. A so-called Z-wave is produced as shown by Fig. 6d by clipping the wave (Fig. 6b) with the wave clipper 0I (Fig. 5) that will be described in detail below. It is clipped at a potential corresponding to the lower dotted line b of Fig. 6b to give the wave (Fig. 6c) and at a potential corresponding to the upper dotted line b" of Fig. 6b to give the wave (Fig. 6d). This wave is amplified by the amplier 84 (Fig. 5) to give the wave (Fig. 6e). The wave (Fig. 6e) is then differentiated by means of the capacitors 86 and 66 and the resistors 8l and 6l and limited in negative amplitude by the diode 08 (Fig. 5) to give the wave (Fig. 6l) which is squared at tube 90 and amplified at 92 to give the wave (Fig. 6g) This wave, (Fig. 6g), is then passed through switch a to the grid I of the cathode-ray tube I and is also attenuated and passed to the grid 8 of the cathode-ray tube 2 (Fig. 2). In this way that portion of the vertical signal wave which occurs during the time interval corresponding to the impulse wave of Fig. 6g will be made brighter than other parts of the sweep cycle. This makes it possible for the observer to identify on cathode-ray tube 2 any particular spark plug that is being examined in expanded time scale on cathode-ray tube I, as explained below. 'Ihe particular spark plug is that one the firing time of which corresponds to the interval in the -cycle represented by the wave of Fig. 6g.

For example, the spark plug impulses of Fig. 6j show the 16th spark impulse intensied, with enough of the previous and the following pulses shown to allow a complete record of the 16th pulse, as examined in more detail on the expanded scale of cathode-ray tube I, Fig. 1a.

The wave clipper mentioned above is shown in Fig. 5. It comprises a potentiometer 98 with two sets of taps 99 and |00 and with the coupled movable contactors IOI and |02 connected, respectively, to the cathode load resistor of the duplex diode 0I, and to the anode return resistor I 00 of the last or right-hand plate thereof. The location of the contacter I02 on a tap |00 determines the potential level location of the lower dotted line b' on Fig. 6b, and the location of the contactor IOI on a tap 09 determines the potential level of the upper dotted line b" on Fig. 6b. Thus by shifting the contacts I'0I and=I02 any segment |00 (Fig. 6d) can be clipped out of the wave (Fig. 6b) corresponding to any one of the spark plugs, so that the signal (Fig. 6g) finally obtained from (Fig. 6d) when applied to the grid of cathoderay tube 2 will make the signal of the plug under examination brighter than the others, and when applied to the grid of cathode-ray tube I will make the corresponding signal thereon clearly visible.

The circuit of Fig. 5 shows facilities for'- examining eighteen spark plugs. In practice, the

g equipment is made more flexible in order to divide the sweep interval into several numbers of segments. For example for testing 8 spark plugs, or other recurrent signals, the voltage divider 96 may be tapped at any suitable intermediate point rather than at the end and .a heavier current passed through the divider. In this way the wave form (Fig. 6b) is divided into 8 equal steps instead of 18. A continuously adjustable potentiometer may be used, since the brightening by grid signal identifies the selected interval.

The wave form of Fig. 6g is passed through the impedance transformer a (Figs. 3 and 5) and is diiierentiated by means of capacitors CIE and CIG and resistor M' to produce the synchronizing pulse |06 (Fig. 6h), which pulse |06 is then fed to the single sweep sawtooth wave generator I0 (Figs. 2 and 3) to yield the spreading Wave form (Fig. 6i), which is ampliiied by the amplifier I0 (Figs. 2 and 3) when the switch 20 contacts are at 35', and is applied to the horizontal plates 5 of the cathode-ray tube I.

The switches 4I (Fig. 3), lia. (Figs. 3 and 5), and Sic (Fig. 5) are connected mechanically as indicated by dotted line e in any convenient way so that when the switch 4I connects the larger capacitor 39 in the circuit the switch da connects the capacitor CI6 in parallel with the capacitor CIB and the switch Sie connects the capacitor 66 in parallel with the capacitor 86'. In this condition the Wave form (Fig. 6g) is differentiated to give the synchronizing pulse (Fig. 6h) which is of variable phase with respect to the pulse |05 (Fig. 6a) so that the sweep signal (Fig. 6i) for tube I is applied to the horizontal deiiecting plates 5 during the interval when the signal from the spark plug being tested is applied to its vertical deecting plates 3. The switches 20 (Figs.l

2 and 3) and 20a (Figs. 2 and 5) are also mechanically connected as indicated by dotted line o so that when the amplifier I4 is connected to the sweep I 9 (Figs. 2 and 3) by switch 20, the switch 20a closes the circuit to apply the signal (Fig. 6g) from the differentiating and squaring unit I8 (Figs. 2 and 5) to the grids of cathoderay tubes I and 2. When the switch 20 closes the circuit to apply the recurrent sweep from generator I3 (Figs. 2 and 3) to the plates 5 of tube I, the switch 20a (Figs. 2 and 5) opens the circuit to the grids 'I and 8 and grounds them.

Although this invention has been particularly described in connection with the test and examination of spark plugs for intemai combustion engines, it is also applicable for investigations wherever the phase of one sweep circuit is to be changed withA respect to another one or with respect to other recurrent phenomena that are to be investigated, and' where it is desired to indicate on an expanded time scale, or otherwise to modify, the phenomena occurring during aparticular interval o'f a cycle.

What is claimed is:

1. An analyzer comprising two cathode-ray tubes, :ir-axis and y-axis defiecting means for the rays of said tubes, and means to render a series of signals visible on one of said c .thode-ray tubes andA means to render one of the same signals simultaneously visible on a larg'er scale on the other cathode-ray tube.

2. An analyzer comprising two cathode-ray tubes, x-axis and y-axis deflectlng means for the rays of said tubes, and means to render a series of recurrent signals from diil'erent sources visible on one of said cathode-ray tubes and means to render one of the same signals simultaneously visible on a larger scale on the other cathode-ray tube.

3. Ihe analyzer of claim l, in which means is provided to render at will any oner of the series of signals visible on the other cathode-ray tube.

4. An analyzer comprising two cathode-ray tubes, :lz-axis and y-axis defiecting means for the rays of said tubes, means to render a series of signals visible on one of said cathode-ray tubes and means to render one of the same signals simultaneously visible on a larger scale on the other cathode-ray tube, and means to identify one of the small scale signals as the one that is on the other cathode-ray tube.

5. An analyzer comprising two cathode-ray 11. The analyser of claim 8, in which the horizontal sweeps of said cathode-ray tubes are synchronised by a signal from an auxiliary shaft of said engine.

13. The analyzer of claim 8, in which the signais applied to the .vertical deiiection plates of said cathode-ray tubes arederived from the spark plugs of said engine.

13. The analyzer of claim 8, in which the signais applied to the vertical deflection plates of said cathode-ray tubes are derived from the spark plugs of said engine and the .recurrence of the respective sweep signals of said cathode-ray tubes is proportional to the number of spark plugs being tested.

14. An ignition analyzer for an internal combustion engine, which comprises two cathode-ray tubes, :xr-axis and z-axis defiecting means for the l rays of Vsaid tubes, and means to render signals tubes, :c-axis and u-axis deiiecting means for the y rays of said tubes, means to render a series of signals visible on one of said cathode-ray tubes and means to render one of the same signals simultaneously visible on a larger scale on the other cathode-ray tube, and means for causing the sweep signal for the larger scale cathode-ray tube to occur at the frequency which is a fraction of the frequency of the signals on the other one.

8. An analyzer comprising two cathode-ray tubes, .r-axis and u-axis deflecting means for the rays oi said tubes, means to render a series of signals visible on one of said cathode-ray tubes and means to render one oi the same signals simultaneously visible on a larger scale on the other cathode-ray tube, and means for synchronizing the sweep signals on both cathode-ray tubes.

'1. An analyzer comprising two cathode-ray tubes. z-axis and y-axis deiiecting means for the rays of said tubes, means to render a series of signals visible on one of said cathode-ray tubes and means to render one oi' the same signals simultaneously visible on a larger scale on the other cathode-ray tube, and means to identify one ci thesmallscalesignalssstheonethatisonthe other cathode-ray tube, said last named means comprising selective grid control of said other cathode-ray tube.

8. An ignition analyser for an internal combustion engine, which comprises two cathode-ray tubes, z-axis and y-axis deiiecting means for the rays of said tubes, and means to render signals from all the spark plugs visible on one of said cathode-ray tubes and means to render one of said signals visible simultaneously on a larger scalemtheothercathode-raytube.

9. The analyser of claim 8, in which means areprovidedtorenderanyoneofthesimals visible on said larger scale cathode-ray tube.4

i0. The analynr of sweepeircuitsofthecathode-raymbesaresynchronisedinaccordancewithsaidsisnals.

claim in 'bien the" from all the spark plugs visible on one of said cathode-ray tubes and means to render oneot said signals simultaneously visible on a larger scale on the other cathode-ray tube, said means comprising a square impulse generator.

15. An ignition analyzer for an internal combustion engine, which comprises two cathode-ray tubes, .r-axis and z-axis deilecting means for the rays of said tubes, means to render signals from all th'e sp'ark plugs visible on one of said cathoderay tubes and means to render one of said signals simultaneously visible on a larger scale on the lother cathode-ray tube, said means comprising a square impulse generator, and means to apply said impulse to the 4grid of one of said cathoderay tubes.

16. The analyzer of claim 8, in which means is provided to produce a synchronizing pulse of variable phase and apply it to the sweep signal generator of one of said cathode-ray tubes.

17. A'n ignition analyzer for an internal combustion engine, which comprises two cathode-ray rays of said tubes, means to tubes, .'c-axis and z-axis deflecting means for the render signals from all the spark plugs visible on one of said cathoderay tubes and means to render one of said signals simultaneously visible on a larger scale on the other cathode-ray tube, and' means for optionally applying a single sweep' to one of said cathoderay tubes during discharge of a set of spark plugs or applying recurrent sweeps to it corresponding to each spark plug discharge. 1

16. In a device of the characater described, a potentiometer having two sets of iixed contacts and two coupled contactors for said sets of contacts movable to difierent contacting positions for contacting respectively with said sets oi' contacts, means for generating a sawtooth wave and feeding it simultaneously to said potentiometer at two distinct potential levels on said potentiometer for iixed positions;

19.1n a'device of the character described. meanstoproduceasawtoothwave atadesired frequency, cliwing means for said wave comprishavingsetsofcontactsand tothepiate ing a potentiometer coupled contactors, a vacuum tube and cathode of which said sets of contactors are connected' respectively to clip said wave at distinct levels for various positions of said contactors and produce pulses simultaneously at predetermined phases with respect to said wave, an oscilloscope, andmeanstoapplysaidpulsestothe control grid of said oscilloscope.

man s. cams'rsrpr.

, cERTFIcATE oF CORRECTION. Patent No. 2,555,565. August 8,5191@ mman S. -cnnIsTALDL It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 5, first column; line 6, for "Fig. 6" second occurrence, read Fig. 6b; page L1., :sec:- ond column, lines 18, 2'? and )4.2 respectively; for "z-axis" 'read' yaxis; and that the said Letters Patent snouldbe read with uns correctionnel-ein that the sa'me mayconform to the record of the case in the -Patent Office.

Signed and sealed this 10th day of October, A. D. 19,414..

Henry Van Arsdale (Seal) Acting Commissioner of Patents.

CBRTIFIGATE oF CORRECTION.

Patent No. 2,555,565. August 3.. 191m.

' fsm s. -cnnIsTAIDL It is hereby certified that er1-oi` appears in the printed specification of the above numbered patent requiring correction as follows: Page 5, first column. line 6, for "Fig, 6" second occurrence, read -Fig. 6b; page u., 4second column, lines l8, 27 and h2respective'1y. for "z-axis" 'read -yaxis; and that the said Letters Patent should be read with this correction` therein that the same may' conform to the record of the case in the Patent Office.

signed and sealed uns 10th day of october, A. D. 19h14.

Henry van Arsdale (Seal) Acting Commissioner of Patents. 

